1. Field of the Invention
The present invention relates to an optical disk device, and specifically to an optical disk device that performs recording on a write-once optical disk.
2. Description of the Related Art
There are two types of recording optical disks. That is, there are a write-once type and an erasable type. As for the write-once type, Te and Bi are used as material for a signal recording surface of the write-once optical disk, and the signal recording surface is irradiated by laser light to melt the surface and form a pit. Alternatively, a thin film of Sb2Se3, TeOx or an organic pigment is used as materials for the recording surface, and the recording surface is irradiated by laser light to vary light reflectance.
A CD-R which is the write-once type is provided with a pre-groove used as a guide. The pre-groove has a center frequency of 22.05 kHz, and slightly wobbles in a radial direction. Address information used at the time of recording is recorded as multi information at the pre-groove by FSK modulation with the maximum deviation being ±1 kHz. The address information is called ATIP (Absolute Time In Pregroove). In the case of the CD-R that is the write-once optical disk, a recording power calibration operation called OPC (Optimum Power Control) is performed prior to recording in order to set the optimum recording power of laser light. A PCA (Power Calibration Area) is provided at an inner side (most inner side) of a data area of the optical disk recording surface. The data area is used for recording various data, and the PCA is a test recording area used for setting the optimum recording power of the laser light. The PCA includes a test area and a count area, and the test area includes 100 partitions. Each of these partitions includes 15 frames.
One OPC operation uses one of these partitions, and test signals are recorded on these 15 frames of the partition by using 15 levels of laser power from the minimum laser power to the maximum laser power. A peak value P and a bottom value B of an envelope of an RF (high frequency) signal reproduced from this test area are detected. A β value is obtained by using the equation: β=(P+B)/(P−B). Recording power at which this obtained β value becomes a predetermined value is regarded as the optimum recording power, and subsequent signal recording is carried out based on the so-determined optimum recording power.
This optimum recording power determination for recording is made because manufactures each manufacture optical disks having different recording characteristics, and therefore, required optimum recording powers of the optical disks are different from each other. Accordingly, when optimum recording power cannot be obtained for each optical disk, an error rate and jitter after recording can greatly increase.
When recording is carried out at a CLV (Constant Linear Velocity) from the most inner area to the most outer area of the optical disk, the OPC may be carried out on the PCA of the most inner area at this constant recording velocity. However, in the case where high speed recording is performed, when the rotational speed of the optical disk is raised, a spindle motor that has high torque is required, resulting in cost increase. Furthermore, in this case, since vibration is generated at the time of the high speed rotation, servo tracking performance becomes inadequate.
In order to realize further higher speed recording with the rotational speed of the optical disk being limited to a certain value, ZCLV (Zone Constant Linear Velocity) recording and PCAV (Partial Constant Angular Velocity) recording have been proposed, and products for such recording have been manufactured. In both ZCLV and PCAV recording methods, high speed recording is realized by using an obtainable linear velocity at an outer part which is higher than the linear velocity at an inner part while the rotational speed of the optical disk is limited.
However, in both cases of the ZCLV recording and the PCAV recording, at the most inner area of the optical disk, it is impossible to obtain the linear velocity that is used for the high speed recoding at the outer part of the optical disk. Accordingly, the OPC for the high speed recording of the outer part cannot be performed at the PCA of the most inner area, and therefore, optimum recording power for the high speed recording of the outer part cannot be obtained.